1. Cribs and children’s furniture: If there’s any chance that you’ll put your children at risk by buying used, just buy new. Used children’s furniture, especially cribs, can be a safety hazard because you can’t be certain of a potential recall or if the crib was installed correctly.

2. Car seats: Even if a used car seat looks OK, damaged car seats aren’t uncommon. Considering that safety technology improves every year -- and the fact that car seats can go for as little as $50 -- buying new is usually the better option.

3. Bicycle helmets: Usually, a crash would only crush the foam inside the helmet casing, so the damage to the helmet may not be visible. However, since helmets are meant to protect against one accident only, buying new would be a safer bet.

4. Tires: Sometimes it’s hard to tell if used tires were once part of a totaled wreck. If they have been in an accident, they’re bound to be unstable and unreliable. Putting your safety at risk for the sake of saving a few bucks just doesn’t add up.

5. Laptops: Because of their portability, laptops are prone to all sorts of abuse and problems. When you buy a used laptop, unless it’s refurbished, you have no idea what it’s been through or when important parts will die on you. You also don’t get the warranties and tech support that come with buying new.

6. Software: Most software comes with a serial number that you register with the company when you activate the software on your computer. If the serial number on your use software has already been registered, you can’t use it again.

7. Plasma and HDTVs: The cost for fixing or replacing the parts on plasma or HDTVs is high. Sometimes, it costs as much as buying a new TV. Considering the repair costs, you’d want to get an extended warranty, but that isn’t an option if you buy your TV used.

8. DVD players: While it’s smart to buy used DVDs, this doesn’t apply to DVD players. DVD players have lasers that will eventually wear out. The cost to repair or replace may cost more than the player is worth.

9. Digital and video cameras: Like laptops, used digital and video cameras are likely to have been dropped and banged around. It may not be obvious, but once the damage kicks in, it’ll be expensive to repair. If you know what to look for in a digital camera, you can get a great new camera without breaking the bank.

10. Speakers and microphones: Speakers and microphones are sensitive audio equipment that don’t stand up well to blasting and mishandling. Like laptops and cameras, the damage may not be obvious, but their performance would be severely compromised.

11. Camera lenses: An SLR camera lens is the most expensive part of a camera. It also directly affects the quality of your images. Any damage to the lens, however slight, will show up in your photos.

12. Photo light bulbs: Not the ordinary light bulbs you use at home. We’re talking about the light bulbs used with photography equipment. They’re relatively expensive, but their life span is short enough that you likely won’t get much use out of them if you buy second-hand.

13. Mattresses and bedding: Just think: You may be sleeping with other people’s mold, mites, bacteria, and bodily fluids. Besides, even the really good mattresses are only supposed to last eight to 10 years, and it’s hard know for sure how old a used mattress may be.

14. Swimsuits and undergarments: This is probably a no-brainer, but it needs to be said: Do not, do not, do not buy used swimsuits or undergarments. They’re worn too close to the body -- someone else’s body -- to consider buying used.

15. Wet suits: Wet suits lose the ability to keep you warm over time. If you’re a scuba diver, or the last owner was one, the constant change in water pressure will eventually wear out the wet suit and make it more likely to tear.

16. Shoes: If you get used footwear, it’s likely they’re already molded to the last owner’s feet. Poor-fitting shoes are not only uncomfortable but can cause all sorts of health problems, as well.

17. Hats: Hats are likely not cleaned before they’re resold or donated. If you buy a used hat, you don’t know if you’re also getting skin infections, old sweat stains, hair products, and other cringe-worthy remnants. Now that’s a deal you don’t want.

18. Makeup: A good thing to remember about used makeup is that it’s a breeding ground for bacteria and a number of contagious diseases. The great deal you found may come with pink eye and cold sores. Instead of buying used, consider making your own beauty products (it's easier than you think) or skip makeup altogether.

19. Pet supplies: Old stains and odors continue to ferment even if used pet supplies are sitting around in storage. If cleanliness is ever an issue, just say no.

20. Vacuum cleaners: Vacuums are among the heavy-duty household appliances that tend to get a lot of use and abuse. They can also cost more to fix than if you bought them new right from the start.